This invention relates to a motor which operates with a rolling, non-sliding action between an armature and a stator.
Electric motors typically include a fixed stator and a rotatable armature, between which electromagnetic forces are produced to cause the armature to rotate. The armature is mounted or carried by bearings to maintain a certain spacing between the armature and the stator and this, of course, gives rise to friction. Also, the further the spacing between the armature and stator, the weaker are the electromagnetic forces.
Electrostatic motors likewise generally include a stator and armature mounted to rotate near or within the stator, where the forces of attraction therebetween are electrostatic rather than electromagnetic. Again, friction and weaker forces between the armature and stator because of spacing are disadvantages of such a structure. Examples of electrostatic motors are shown in U.S. Pat. Nos. 735,621, 3,297,888, 3,517,225 and 4,225,801.
A machine or device called an electrostatic linear actuator is disclosed in Fujita, H. and Omodaka, A., "Electrostatic Actuators for Micromechatronics", IEEE, Microrobot and Teleoperators Workshop, Hyannis, Mass., Nov. 9-11, 1987. This device consists of a plane wafer with striped electrodes spaced apart in an insulation layer overlying the top of the wafer. A cylindrical electrode/roller is positioned on top of the insulation layer to roll back and forth as successive ones of the striped electrodes are activated or charged (and then discharged). Various alternative arrangements of electrostatic linear actuators are described in the reference, but in each arrangement, the electrode/roller rolls back and forth, stopping and starting at each end of the insulation layer.
Several proposals have been made for a type of machine in which an armature or roller rolls inside a cylindrical cavity as a result of electromagnetic forces being successively produced about the perimeter of the cavity. See, for example, U.S. Pat. Nos. 2,561,890, 4,728,837 and 4,482,828, German Patent No. DAS 1132229, and Swiss Patent No. 159,716. Disadvantages of the use of electromagnetic forces, which the devices in all of these references do, are that the devices are generally quite bulky and not easily miniaturized, and only limited types of materials are available for use as device components, e.g. armatures, and these materials are generally quite heavy, making the entire device heavy.